Germinability of seed crops steeped at varying durations and inoculum concentrations of cultures of growth promoting rhizobacteria

The expected increase in agrochemical usage as a result of the projected increase in the world’s population in the coming years will further raise the specter of environmental damage and health challenges. This study aimed to evaluate the effects of steeping duration and initial inoculum concentration sequentially on the growth promotion potential of some bacterial species viz-a-viz five economic crops (cowpea, soybean, sorghum, sesame, and okra) in Nigeria. For the steeping-duration experiment, the different surface-sterilized seeds were steeped for increasing durations (1, 2, 3, 4, and 5 h) in broth cultures of five rhizobacterial isolates: Serratia liquefaciens, (OP830504), S. liquefaciens (OP830503), Providencia rettgeri (OP830491), P. rettgeri (OP830498), and Bacillus cereus (OP830501). The seeds were planted in transparent containers that contained blotters and incubated for 8  days. Similarly, the experiment for inoculum concentration was carried out using different initial bacterial concentrations (4:1, 3:2, 2:3, 1:4, and 0:5 water dilutions). At the end of both experiments, final germination percentage, mean germination time, germination index, and vigor index were estimated. Although, results showed that optimal steeping duration was largely restricted to 1, 2, or 3 h, especially for final germination percentage and seedling vigor index, no consistent trend was observed between concentration of inoculum used for treatment and the germinability parameters measured. This study highlights the general adequacy of a short steeping duration under low initial inoculum concentration for biopriming experiments involving the use of bacterial inoculums.